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G3 model M5521 no power on & analog board arcing sounds

belzrebuth

Well-known member
I've got a G3 that was given to me sometime ago and never got around messing with it.
The previous owner reported that it has a power supply of sorts.
I tried to power it on today and no green light comes up and I see no CRT activity other than some arcing sounds near the power plug.
I have removed the plastic covers but the motherboard and the analog board are still attached so I can hopefully understand what's going on.
The internal PRAM battery is missing.
From what I've seen there is no visible damage on the analog board but I could be wrong since I haven't completely dissasembled the unit.
Any ideas on what might going wrong.
The computer seemingly powers up for a while arcs for 20 seconds or so and then maybe shuts off because if I press the power on button after a minute or so I get the same behavior all over again.
It could be a short somewhere so could it be something powering off the computer to protect it from further damage? I really don't know.
Any suggestion would be welcome.
 

Byrd

Well-known member
Hi,

What model G3 - sounds like an AIO? If so it sounds more like flyback transformer over PSU
 

belzrebuth

Well-known member
It's an EMC 1857 (color= blue and it has firewire ports and a vga connector).
It never booted in my hands so I don't know about proccessor speed etc but should be a 350MHz.

Not sure how to test the flyback and I don't have a high voltage probe so I don't think I can just measure stuff there with a multimeter or a scope.
Are there any schematics available for it?
I'd really like to get it going since I've never owned a G3 iMac.

From a quick search I've seen this is a common problem with iMacs of this era but most solutions are pretty vague like replace analog board or whatever.
Are there any troubleshooting steps in order to verify where my problem might lie?
I don't get anything on the CRT so that might indeed indicate there is no high voltage on it but I'd still like to troubleshoot it a bit more because I think my chances of finding a suitable flyback transformer are pretty slim.
 
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